The present invention relates to a method of controlling the feed of paper sheets in a copier of the type having an automatic document feeder (ADF).
An ADF is a common equipment with many modern copiers and is provided on a glass platen for copying multiple documents efficiently. A copier with an ADF may be so constructed as to start feeding a paper sheet from a paper tray or similar storage immediately in parallel with the feed of a document by the ADF, thereby eliminating the loss of time ascribable to a paper feed waiting time to a significantly reduce the overall copying time. In practice, however, a copier with an ADF often encounters misfeed of a document and therefore cannot be entirely freed from jams due to the misfeed. If a paper sheet has already been fed from a tray or the like when a misfeed of a document occurs, a reproduction of the document will be locally or entirely missed out on the paper sheet resulting in a copy which is practically unavailable, i.e. waste copy. More specifically, since various units adapted for a sequence of copying processes such as charging, exposing, developing, transferring and fixing processes are not deactivated even when a document has been misfed and the feed of a paper sheet has begun, the copying processes are effected with the paper sheet wastefully. This brings about a problem that a paper counter associated with the paper tray, for example, counts up even such a waste copy. Another problem is that the waste copy is distributed to a predetermined bin of a sorter together with acceptable copies, rendering handling of the resulting copies troublesome. Furthermore, when a two-sided copy mode is selected, the waste copy is transported to an intermediate or two-side tray and therefore also results in the need for troublesome handling.
In light of this, there has been proposed a copier the paper feed timing of which is controlled such that whether or not a document misfeed has occurred in an ADF is determined and, only if it has not occurred, a paper sheet is fed from a paper tray. This kind of control method, however, wastes time in awaiting the decision as to the document feed condition and therefore increases the overall copying time. Such a waste of time is critical especially when a great number of documents are continuously copied.